1. Field of the Invention
The invention relates generally to golf clubs and, more particularly, to a golf club head in which the center of gravity, balance, and weight are customizable and can be altered to suit changing course conditions, weather conditions, and/or other user requirements.
2. Description of Related Art
Golfers have long recognized that they could alter the weight, balance, and performance characteristics by selectively adding weight to club heads. Typically, weight is added by applying thin strips of lead tape with an adhesive backing to the club head. In this manner the swing weight is increased and the center of gravity (CG) is altered to change the dynamics of the head during the swing and, therefore, the ball flight characteristics after contact. The location of the lead tape, however, is generally limited to the back, crown, and/or sole of the club heads where it would best stay affixed and not alter the look of the club, but this limits the adjustability options available to the golfer. For example, the lead tape could not be put on the face of the club to move the CG closer to the front of the club which is more desirable to some golfers who want the club to be easier to “work”, i.e., to shape shots both in a left-to-right manner and in a right-to-left manner.
Furthermore, this use of lead tape was generally an additive process whereby the swing weight and total weight of the club was increased, often times negatively effecting other performance characteristics of the club. Some golfers overcame this obstacle by grinding down or using other means to reduce the weight of the club. However, this often damaged the protective finish of the club or the shape and configuration intended by the club designer, negatively affected the after-market value of the club, and was difficult and time consuming for the golfer to adjust.
Furthermore, manufacturers of golf clubs have encountered problems when attempting to manufacture individual clubs to identical specifications because of variances of the individual components themselves and when assembled together. Generally, manufacturers build clubs to a weight at, or slightly below, a targeted weight specification and then add additional weight in the head and/or the shaft to increase the total weight and/or the swing weight to the desired specification. Additional weight is commonly added by pouring lead powder into the bottom of the shaft and sealing the shaft with a cork or other means. Alternatively, lead powder has been mixed with putty, epoxy, or other materials that are inserted into the end of the shaft of the assembled head and shaft to facilitate this final weight adjustment by the manufacturer. This method, however, alters the CG of the club away from the optimal location, adversely effecting performance and feel.
Additionally, a common practice has been to inject a hot melt glue or similar material into a hole in the club head during final assembly to arrive at a prescribed swing weight. The location that the glue puddles and adheres to the inner walls is determined by the orientation of the head while the glue is still hot and fluid. Furthermore, this technique has been used to customize the center of gravity of the club head for specific golfers' needs. The location of the glue, however, is generally limited to one broad area due to the closed process, and once the glue is set, the glue is not adjustable.
Several methods have been attempted to create a golf club that allows the weight, balance, and CG of golf club heads to be altered. One example is disclosed in U.S. Pat. No. 6,254,494 to Hasebe, et al. (hereinafter “Hasebe”), entitled, “Golf club head”. The weights, which effect CG location and club head dynamics during the swing and the ball flight after contact, can be changed during manufacturing. Once manufactured, however, the weights can not be altered or be customized for individual needs. Therefore, a club head must be manufactured for each desired weighting configuration.
Another example is disclosed in U.S. Pat. No. 6,248,025 to Murphy, et al. (hereinafter “Murphy”), entitled, “Composite golf club head and method of manufacturing”. Murphy discloses a weight strip within a ribbon of the body of the club head. Weights in the form of densified loaded films and/or ribbons of material denser than the primary composite material of the head are added to the internal structure assertedly to increase the forgiveness and playability characteristics, including the energy transfer. Murphy discloses that the location and configuration of the weights can be changed during manufacture to achieve varying characteristics, but, once the weights are added and the club head is completed in manufacturing, the weights can not be altered.
Yet another example is disclosed in U.S. Pat. No. 6,206,790 by Kubica, et al. (hereinafter “Kubica”), entitled “Iron type golf club head with weight adjustment member”. Kubica assertedly discloses a weight adjustment member located within a secondary cavity within the back of a cavity back iron golf club head. The weight adjustment member is said to be chosen from a plurality of weight adjustment members to overcome variances in manufacturing tolerances and to adjust golf club swing weights to custom fit various golfers' requirements. The weight adjustment member, however, does not allow the position of the CG to be altered.
Yet still another example is disclosed in U.S. Pat. No. 3,652,094, to Glover (hereinafter “Glover”), entitled, “Golf club with adjustable weighting plugs”. Glover assertedly discloses the use of threaded weight plugs to alter the CG. The location of the CG in Glover, however, is limited to the position of the threaded cavities. Similarly, U.S. Pat. No. 5,050,879 to Sun, et al. (hereinafter “Sun”), entitled, “Golf driver with variable weighting for changing center of gravity”, assertedly discloses three cavities that are sealed by a cover plate in the sole where weight members can be selectively installed. However, the user's options for the location of the weight members are limited to adjustment between the three predetermined cavities, in the horizontal plane from heel to toe, and near the sole only.
Yet still another example is disclosed in U.S. Pat. No. 6,306,048 to McCabe, et al. (hereinafter “McCabe”), entitled, “Golf club with weight adjustment”. McCabe assertedly discloses one or more weight chambers that the golfer uses to adjust the weight and CG of a club to customize it to his or her own needs. A filler material is used to set the weights in position. This method, however, limits the weights and weight changes to the location of the internal weight chamber, and, once the filler material is set, the golfer can no longer adjust the weight or center of gravity.
Therefore, there is a need for a golf club head with a customizable CG that allows the CG to be altered by a golfer and/or the manufacturer.